The façade, as the exterior cladding of a building, is an essential component which provides waterproofing, thermal isolation, light transparency and structural independence against environment actions. The vertical member, named mullion, is the dominant wind load-bearing structural member in this façade system. Even though aluminium is a durable material, the conventional aluminium frame is weak in thermal performance. On the other hand, timber frames are preferred by architects due to their aesthetic appearance and sustainability. Therefore, an innovative composite mullion was developed in this study using aluminium and timber to achieve the best features of both materials. An experimental study was also conducted to verify the structural performance of the composite mullion. Four-point bending tests were performed to investigate the bending behaviour of the newly developed product. The test results showed that the section moment capacities of the composite mullions are greater than the traditional aluminium mullions.